The article in the popular Swedish newspaper Aftonbladet alleging the Israel Defense Forces were involved in organ theft was the latest and most heinous example of an increasingly familiar phenomenon: classic anti-Semitic tropes and expressions of open hostility to Jews turning up in statements by members of the European liberal left.

This process derives from the growing popularity of openly anti-Semitic, Islamist organizations in the Middle East, and the accompanying regional political culture. These Islamist organizations are seen by a growing part of the Western left as partners for civilized dialogue. Some toward the more radical fringes see them as natural comrades in the joint battle against common enemies.

It is normal to give a respectful hearing to a friend’s allegations and claims. One is not accustomed to believing that respected friends have a tendency for pathological lying and paranoia. And the fact is that if you have decided to make friends with the regional political culture of anti-Israel militancy, you are going to be hearing an awful lot of claims of the kind that appeared in Aftonbladet.

Both oppositional and mainstream political discourse in the Middle East afford numerous examples of the crudest anti-Jewish stereotyping and sentiment. There is Hezbollah, which invented the curious allegation that 4,000 “Israelis” failed to turn up for work at the World Trade Center on September 11. The accusation was first broadcast on its television station Al-Manar, which three years ago also screened the Syrian-produced series “Al-Shatat” (“The Diaspora”), which contained dramatic depictions Jews making matzot with the blood of Christians. Officials from the organization have referred to Jews as a “lesion on the forehead of humanity,” along with a variety of other medical metaphors.

There is Hamas, whose Al-Aqsa TV station in April broadcast a play from the Islamic University in Gaza that contained a Jewish father exhorting his son to “drink the blood of Muslims,” and whose very founding document references the “Protocols of the Elders of Zion” to prove the nefarious plans of the Jews.

There is of course the Iranian president, with his Holocaust denial cartoons and conferences. There is the Egyptian, Qatar-based, so-called “reformist” cleric Yusuf Qaradawi, who praised Adolf Hitler for “punishing” the Jews on one of his popular broadcasts on Al Jazeera, and so on. And on.

Thus far the Middle East. In the past, Western leftist supporters of the Palestinians adopted the language of secular Palestinian nationalism. The latter tends to avoid the worst excesses of anti-Jewish rhetoric, at least in the English-language statements of its spokesmen. When it recalls the motifs of classical anti-Semitism, it tends to direct them at “Zionists,” rather than at Jews per se.

But secular Palestinian nationalism is in decline. The radicals who increasingly set the tone today come dressed in Islamic religious garb. They care little for the niceties of political correctness. And so the many Westerners whose search for a cause leads them for whatever reason to the Palestinians are today speaking in tones and adopting stances that would have been quite unimaginable even a decade ago.

The Aftonbladet article by Donald Bostrom, with his tales of an international conspiracy involving IDF organ thieves and ultra-Orthodox rabbis in New Jersey, is only one example. Earlier in August, Holland’s largest daily newspaper, De Telegraaf, published an interview with medical journalist Desiree Rover, who asserted that the global swine flu pandemic was the result of a “Khazar Jewish” conspiracy to reduce the world’s population.

And who can forget Jostein Gaarder, Norwegian author of the best-selling novel “Sophie’s World,” who in late 2006 stated in an article in the major Aftenposten newspaper, “For two thousand years, we have rehearsed the syllabus of humanism, but Israel does not listen,” before helpfully (if inaccurately) pointing out, “It was not the Pharisee who helped the man who lay by the wayside, having fallen prey to robbers. It was a Samaritan; today we would say a Palestinian.”

These tones are both new and very old. They are not the language of humanism and the enlightenment. They are instantly recognizable to anyone familiar with the tone of anti-Israel literature in the Middle East. They are also redolent of another, older Europe. These stalwarts of the bon ton left are adopting ideas whose original purveyors were situated, and are still situated, on the extreme right of the political spectrum. The ideas in question, which hark back to medieval Christianity, migrated from the European radical right to the Middle East, from where they have now migrated back to Europe, finding a new political home in the process.

Irony aside, a British organization that monitors anti-Semitism recorded an eight-fold increase in anti-Semitic incidents in the U.K. that coincided with the launch of Operation Cast Lead last December. It is hard to draw causal lines in such cases, of course. The British citizens who write “slay Jewish pigs” on London walls, or the foreign activists who chanted “Jewish racist pigs” at a demonstration in the Jerusalem neighborhood of Sheikh Jarrah last month, may well never have heard of Bostrom, Rover or Gaarder. Still, all these instances taken together confirm that a new and old and ugly spirit is abroad.